Rapportive is a Gmail plugin, which replaces the Gmail sponsored links with useful contact details.

To enable Rapportive in Mailplane, please try these steps:

Go to "Preferences > Accounts" and click the "Plug-ins" tab

Enable the "Rapportive" setting

By using Rapporitve "Raplets", Rapportive can integrate web services like "MailChimp", "Batch Books", and "Brightpearl" to supplement the information in the side bar. Rapportive also provides an API to custom built your own "Raplet".